Torque motor



May 31, 1960 G. D. GEBHART 2,939,055

TORQUE MOTOR Filed April 25. 1958 INVENTOR. GEORGE D. GEBHHRT BY .D HM

AGENT 2,939,055 TORQUE MOTOR -'George D. Gebhart, Los Angeles, Calif., assignor to Herman B. Graves, Culver City, Calif.

Filed Apr. 25,1958, Ser. No. 731,042 12 Claims. (Cl. 317-188) tion withservo-mechanical systems, it is necessary to apply. a'considerable force in order to operate valves, relays and the like. A suitable type of mechanismconsists of an armature, generally in bar form, and forming part of the magnetic circuit of an electro-magnetic assembly. The armature is caused to deviate from its rest position by the energizing of the electro-magnets concerned, whereupon a considerable force is available, generally over arelatively short distance of travel, and thus may be used for the operation of various especially under automatic control, and in particular, valves associated with hydraulic systems and the like. Mechanisms of this type have come to be known in recent years as torque motors, and since this term is used in the trade in connection with the sale of such devices, it is adopted here.

In order that the armature operating the driving mechanismmay have a zero position to which it returns when the electro-mag'nets are not energized, it is usual to cause the armature to operate against a restoring force, often embodied in the armature support. The difiicultyencountered in providing a suitable support and restoring force for the armatures of torque motors has been very great, and torque motors having mechanical hysteresis within desirably low limits are uncommon. Frequently the very mechanical elaboration employed to solve the problem is itself the source of mechanical lag or hysteresis, so that the armature remains displaced on one side or the other of its average rest point depending upon the direction and extent of its last operating displacement. The complexity of the suspensions heretofore adopted likewise makes for poor reproducibility, so that it is very diificult and costly to produce a number of like torque motors all having operating characteristics within a predetermined narrow range without the necessity of individual, careful adjustment. Torque motors arewidely used in very critical applications, in particular, in servo-mechanisms in connection with 7 military craft of alltypes, including submarines and aircraft, and are routinely used in connection with guided missiles and industrial controls generally. It will readily be appreciated, therefore, that the mechanical and electrical requirements are severe.

An object of this invention is to provide a construction for a torque motor'whereby hysteresis of the armature position is reduced to an extent heretofore thought virtually impossible. --Another object of the invention is to provide a construction of torque motor which lends itself to mass production of many units all having precisely equal mechanical and electro-magnetic properties.

associated devices,

Another object of the invention is to provide a torque motor which is adapted to relatively easy manufacturing and assembly.

Other advantages of the invention will become apparent as the description thereof proceeds.

In the drawing,

Figure 1 is a side view, partly in section, of my improved torque motor.

Figure 2 is a top view of the device shown in Figure 1, with part of the armature broken away so as to show the underlying construction.

Figure 3 shows an alternative form of support rod. Returning now to Figures 1 and 2, 1 designates a base which may be of suitable metal and preferably of a magnetic nature, to be discussed in greater detail hereinbelow. Supported by the base are a first solenoid 2, and a second solenoid 3. The solenoids may be of conventional construction, comprising a bobbin or coil of magnet wire surrounding a central core, again of suitable magnetic material. I prefer to form the cores 4 of the solenoids integral with the base, as this gives more rigid construction, although it will be understood that the cores may be welded or otherwise affixed to the base. Just above the tops of the solenoids, spaced sufliciently to provide a suitable air gap and thereby permit some mechanical movement, is an armature 5, which is best made in bar form, as appears from the drawings. The armature likewise is made of magnetic material, and it will be apparent that a magnetic circuit is formed by the armature, the cores of the solenoid, and the base.

The armature is supported by a rod -6, which as appears from Figure 1 is of generally cylindrical shape, having conical ends and a cylindrical section therebetween. The lower conical end seats in a boss or extension 7 which is preferably formed, integral with the base, while the upper end of rod 6 is seated in a conical seat more or less centrally located in the armature 5. While the support rod 6 will generally be of magnetic material,

such as steel, and will thereby form an additional branch of the magnetic circuit of the entire assembly, I prefer to use the boss 7 itself as efiiciently as possible to complete this branch of the, magnetic circuit, for which purpose I bring it nearly up to the armature 5, as appears in the drawings. In actual manufacture, a bar of material may be subjected to a multiple milling operation which leaves a flat base 1, the two solenoid cores, and the boss or extension 7. The latter is then centrally drilled, the upper portion oversize so as to provide clearance for the support rod, while the lower portion is reamed with a conical reamer so as to form a conical seat therein. It is convenient to provide a drive rod 8 for taking power from the torque motor, and I prefer to pass this drive rod through a small hole bored lengthwise in the solenoid cone 4, so that it may operate any desired device to which the base of the torque motor 1 is attached. The drive rod may be rigidly held within the armature by a set screw 9, and as may be seen from the drawing, may have two flat portions ground in which are mutually perpendicular so as to provide bending compliance while maintaining longitudinal rigidity.

In operation, the solenoids are energized in a well-, known manner by passing a current through the coil of each. The windings may be connected so that one solenoid attracts while the other repels, whereupon the torque on the armature 5 is additive; or-the torque motor may be connected so as to respond to the difference in two energizing signals applied to the solenoids separately. In

short, generally circular arc while the armature passes from one extreme of its motion to another.

While the various metallic portions of the torque motor may all be made of ordinary magnetic material such as soft steel or iron, I prefer to form all of the parts, with the possible exception of the support rod 6, of a magnetic material having as little remanance as possible. A number of such alloys are commercially available, and for the most part contain more or less nickel. Suitable alloys are described on pages 36 and 37 of US. National Bureau of Standards Circular 485 entitled, Nickel and Its Alloys. The reason for selecting such alloys is to produce as little hysteresis in the torque motor as possible. Thus, when the solenoids are not energized, the armature should return to a rest position which is invariant and unaffected by any previous excursion of the armature to one side or the other. The 50 percent-nickel iron alloy described on page 36 of the said Circular 485 and referred to therein as Hypernik is especially suitable.

It may be desirable in some instances to provide a support rod in which the portion between the conical ends is not fully cylindrical, but has one or more fiat portions. A suitable configuration is shown in Figure 3 wherein the shank portion referred to is approximately rectangular in cross section. Where tolerances for output for a given electrical input are very narrow, the flat portions of the support rod shown in Figure 3 are convenient for grinding' down so as to achieve the desired resistance to bending, whereby a number of torque motors of equal response may be produced.

It will be apparent that a mode of construction has been provided which lends itself to extraordinary ease of manufacture and assembly, as well as reproduction of precisely controlled operating characteristics. With the conical ends and the corresponding seats being carefully made, the torque motor is assembled by merely twisting and/ or pressing the armature on to the support rod, whereby the attachment may be made as firm as desired. Units made in accordance with my invention have been extensively tested and have been found to be extraordinarily resistant to inadvertent disassembly during use.

Some nickel alloys, as described in the Bureau of Standards circular cited, combine both low remanance and good mechanical properties, and may be used for the material of the support rod 6. For less exacting requirements, it may be permissible to utilize a magnetic material which is magnetizable to some extent as a permanent magnet, suchas for example ordinary drill rod, since the contribution of the support rod to the total magnetic circuit is relatively slight and can often be ignored and also can be nearly cancelled out by proper polarization.

While specific embodiments of any torque motor have been described and illustrated in detail, it will be understood that the invention is capable of numerous modifications, changes, and other elaborations within the broad scope of the invention, as defined by the claims which follow.

Having described the invention, I claim:

1. In a torque motor, a base, an armature of generally bar form spaced from said base and parallel thereto, a first solenoid and a second solenoid, said solenoids interposed between said base and said armature and forming an air gap against said armature, yieldable support means intermediate said solenoids joining said base with said armature, said support means comprising a rod having two ends, one end of which is rigidly aflixed to said base and the other end of which is rigidly affixed to said armature, said rod being free to bend intermediate of said ends so as to permit said armature to be displaced laterally and angularly from its rest position with respect to said base.

2. In a torque motor, a base, an armature of generally bar form spaced from said base and parallel thereto, a first solenoid and a second solenoid, said solenoids interposed between said base and said armature and forming an air gap against said armature, said base bearing a cone seat, said armature having a cone seat, said armature being yieldably supported by a rod means having a first conical end rigidly aifixed in said cone seat of said base and having a second conical end rigidly affixed in said cone seat of said armature, said rod being free to bend intermediate of said ends so as to permit said armature to be dis:- placed laterally and angularly from its rest position with respect to said base.

3. The torque motor of claim 2 wherein said rod means has a substantially cylindrical configuration intermediate said conical ends.

4. The torque motor of claim 2 wherein said rod means has a substantially cylindrical configuration of round section intermediate said conical ends. 5. In a torque motor, a base, an armature of generally bar form spaced from said base and parallel thereto, a first solenoid and a second solenoid, said solenoids interposed between said base and said armature and forming an air gap against said armature, a boss on said base bearing ,a cone seat, said boss extending to form an air gap with said armature, said armature having a cone seat centrally located therein, said armature being yieldably supported by a rod means having a first conical end rigidly afiixed in said cone seat of said boss, and having a second conical end rigidly affixed in said cone seat of said armature, said rod being free to bend intermediate of said ends so as to permit said armature to be displaced laterally and angularly from its rest position with respect to said base.

6. The torque motor of claim 5 wherein said rod means has a substantially cylindrical form intermediate said conical ends.

7. The torque motor of claim 5 wherein said rod means has a cylindrical form of substantially round cross section intermediate said conical ends.

8. The torque motor of claim 3 wherein said armature has attachment means for a drive rod adjacent at least one end thereof.

9. The torque motor of claim 6 wherein said armature has attachment means for a drive rod adjacent at least one end thereof.

10. In a torque motor, a base, an armature of generally bar form spaced from said base and parallel thereto, a first solenoid and a second solenoid, said solenoids interposed between said base and said armature and forming an air gap against said armature, a boss of magnetic material on said base intermediate of said first and second solenoids and bearing a cone seat, said boss extending to form an air gap with said armature, said armature having a cone seat centrally located therein, said armature being yieldably supported by a rod means having a first conical end rigidly afiixed in said cone seat of said boss and having a second conical end rigidly afiixed in said cone seat of said armature, and said boss being recessed longitudinally above the cone seat of said boss so as to house said rod means.

11. The torque motor of claim 10 wherein said rod means has a substantially cylindrical form intermediate said conical ends.

12. The torque motor of claim 10 wherein said rod means has a cylindrical form of substantially round cross section intermediate said conical ends.

References Cited in the file of this patent UNITED STATES PATENTS 2,398,681 Weber Apr. 16, 1946 01 Langer July 20, 1948 2,802,079 Duffing Aug. 6, 1957 

